Neuro 95: Foundations of Neuroscience History & Philosophy Module

1. Neuro 95:Foundations of NeuroscienceHistory & Philosophy Module Brian Keeley Philosophy, Pitzer College Office: Broad Hall 107 Dion Scott-Kakures Philosophy, Scripps College Office: Humanities Bldg #215 Lecture 5

2. Bechtel & Mundale

3. Multiple Realization, again • This paper is a direct assault on the concept of multiple realizability. They think the best response to this worry is simply to deny it, in fact, occurs in any robust or interesting sense. According to them, it certainly doesn’t have any important effect on how real neuroscience is done. • According to B&M, real neuroscience is done comparatively, and comparative neuroscience is not hampered by MR in the way functionalists worry.

4. Comparative Neuro. • “If the gloomy implications of multiple realizability were to be taken seriously, one would not expect results based on comparative neuroanatomy and neurophysi-ological studies to be particularly useful in developing functional accounts of human psychological processing” (p. 178) (But this is far from the case, in fact, they argue).

5. Korbinian Brodman • Cytoarchitectonics: “The gain in brain lies mainly in the stain”; use staining and nerve tracing techniques to map the brain. • Different parts of the cortex contain different kinds of neurons and areas are connected to one another in identifiable patterns. (1868-1918)

6.  Left Lateral Cortex Right medial Cortex

7. How were the maps constructed? • Answer: Comparatively. • “Thus, in defending the claim of six different layers in cortex, he reports preparations made from 55 species ranging over 11 different orders of mammal, and presents diagrams from the cat, wallaby, kinkajou, and rabbit, as well as the human. … From these maps he argues that there is a similarity in the overall patterns of parcellation, constancy in broader regions … across species, and persistence of individual areas” (181).

8. Shows that Brodman is not unusual • Use of lesioning studies and stimulation studies ALSO work together comparatively to figure out how the brain works • Dion talked a bit about Ferrier’s lesion work (and Gall’s thoughts about it) earlier.

9. Wilder Penfield • Direct brain stimulation: In patients requiring brain surgery, electrically stimulate the cortical surface and see how the patient responds. • Important technique still used today in order to identify and spare the more crucial brain regions during brain surgery. (1891-1976)

10. Penfield’s Homunculus

11. Where we stand today

12. So, why were we ever taken in? • Assume for a moment that B&M are correct. If they are, they owe us an explanation of why so many were so taken in by this “multiple realizability” argument in the first place. • Their answer, we were fooled by an easy-to-overlook “grain-size” difference.

13. So, why were we ever taken in? • Usually, when we talk about high-level, psychological functions, we use rather gross, general terms. And, when we talk about neurobiology, we tend to use rather fine-grained terms. • So, we might talk about “hunger” leading to “food-seeking and consumption behavior” (notice how general that is). But when we talk about neurons, we notice all the little differences in the tiniest details. • B&M argue that if we hold grain-size constant multiple realizability goes away.

14. Zawidski & Bechtel

15. Different model of reduction • The story here is reductionist, but isn’t the DN-model of reduction. • They endorse an approach that looks for mechanistic explanation through decomposition and localization. • That is, reductive explanation is not about scientific laws… • …its about identifying mechanisms, figuring out how those mechanisms work (decomposing them), and then figuring out where they happen (localization)

16. Three “Strands” • Z&B see that Gall’s legacy lives on in three different strands of contemporary research: • Direct localization of whole mental functions (found in Fodor’s modularity theory) • Top-down functional decomposition(much cognitive psychology, AI, and many philosophers, such as Lycan & Sterelny) • Interactive decomposition & localization(cognitive neuroscience) • (Hint: it’s the third strand that they think is closest to the mark)

17. 1) Direct localization • Closest to the spirit of Gall • Sit down and identify mental phenomena (language, memory, etc.) • Figure out how they are related to one another • Identify where they happen in the brain. • (Notice: you do your psychological theorizing first, and only then try to find those things in the brain, if at all)

18. 2) Top-down functional decomposition • This methodology takes mental functions and “chops them up” into parts that together explain the function. • For example, language comprehension: • You need a mechanism to differentiate the sounds (phonology), and another to identify how the sounds go together as words, and something figure out the meaning of words (semantics) and something else to figure out the grammatical clues, and so on.

19. 2) Top-down functional decomposition • But, it’s “top-down”… you start with the mental phenomenon and then divide it up. • Neuroscience may have little or nothing to do with it.

20. 3) Interactive decomposition • This is like top-down functional decomposition, in that you take mental tasks and divide them up into their component sub-tasks. • However, unlike top-down functional decomposition, here it is done in consultation with neuroscience (Churchland’s “Coevolution”?) • The result is a psychological theory of mental phenomena that coheres well with the findings of neuroscience • Hence, its status as a reductionist theory.

21. 3) Interactive decomposition • The example they discuss at length is recent work in the hot-topic research area of “attention” • The “cocktail party” effect. Notice how quickly you “tune in” when somebody in another part of the room mentions your name. • That’s attention at work. • B&Z discuss recent work in this area in detail, showing how the different theories of attention have interacted with one another. • They believe it exemplifies their approach.

22. 3) Interactive decomposition • Particularly interesting is the shift from a “bottle-neck” conception of attention (which came from a top-down approach) to a “spot-light” conception (which came from brain studies). • They describe the various studies and theories much better than I can, but perhaps there are questions about any of this?